1. Field of the Invention
The present invention relates to a magneto-system firing apparatus, and more particularly to a magneto-system firing apparatus mounted on an aircraft and having a breaker failure detecting portion which is capable of detecting an abnormal state of the make/break operation of the breaker.
2. Description of the Related Art
In general, a battery type firing apparatus is applied to an engine for an automobile, but a self-generatable magneto-system firing apparatus is used in the aircraft from the viewpoint of safety.
As shown in FIG. 8, the magneto-system firing apparatus of this type includes a permanent magnet 11 disposed on a rotary shaft 10 that interlocks with a crank shaft of an engine, a primary coil 13 that forms an ignition coil wound around an iron core 12 which is so disposed as to surround the permanent magnet 11, a secondary coil 14 larger in turn ratio than the primary coil 13, a cam mechanism 15 connected to the primary coil 13 and disposed on the rotary shaft 10, and a mechanical breaker 18 which is driven by the cam mechanism 15, and makes intermittent a current generated in the primary coil 13 due to the make/break operation of a contact point 17 which is abutted against the surface of the cam 16 or spaced apart from the cam 16.
In the magneto-system firing apparatus 19 of this type, in the case where a low-voltage current is generated as an inductance current in the primary coil 13 due to the rotation of the permanent magnet 11 interlocked with the rotation of the crank shaft, the breaker 18 is driven by the cam mechanism 15 so as to be actuated so that the contact point 17 is opened, and the low-voltage current in the primary coil 13 is broken, as a result of which a high-voltage current is induced in the secondary coil 14, and the high voltage is applied to spark plugs (not shown) disposed in the respective cylinders through a distributor 20 to cause spark discharge at spark gaps and fire an air-fuel mixture in the cylinders, thereby driving pistons. In the figure, reference numeral 21 denotes a capacitor and 22 is a spark plug.
In the breaker 18 thus structured, since the above contact point 17 is repeatedly physically abutted against and spaced apart from the surface of the cam 16 to make and break the current that flows in the primary coil 13, there is a possibility that the contact point 17 is burned and damaged while it is used. In the case where the contact point 17 is thus burned and damaged, even if the crank reaches a predetermined rotating angle at a spark timing, the breaker 18 does not appropriately conduct the make/break operation, so that the current in the primary coil 13 is not broken, with the results that because the high-voltage current is not induced in the secondary coil 14, there is a case in which the spark discharge does not occur in the spark plug, and the air-fuel mixture within the cylinder is not fired.
In order to prevent the above situation, in an engine for an aircraft, there is formed a so-called dual ignition system having two magneto-system firing apparatuses 19 for each of the piston cylinders from the viewpoint of safety. A pilot is under an obligation to conduct the stop operation with respect to the two magneto-system firing apparatuses 19 mounted on the respective cylinders, to confirm that the number of revolutions of an engine is lowered a certain degree, and to confirm whether or not the respective magneto-system firing apparatuses 19 are normally actuated, before every time the aircraft takes off. The above confirming operation must be conducted every time before flying which is troublesome.
Also, at the time of inspections on the ground, the operation of inspecting the breakers is periodically conducted every several tens hours, and in the case where the contact point 17 is burned and damaged, it is necessary to replace the breaker 18 with a new one. Thus, the inspecting and maintaining operation is also complicated. Under the above circumstances, up to now, it is desirable to provide a means for detecting the burning damage and deterioration of the breaker 18 of the magneto-system firing apparatus 19 at a real time.
However, it is difficult to provide the means for detecting the abnormal operation of the breaker 18 for the following reasons.
In order to judge whether or not the contact point 17 of the breaker 18 is normally actuated, there is proposed, for example, a manner in which a circuit that can detect the resistance value of the breaker 18 is disposed in the breaker 18, and the respective resistance values at the make/break time of the contact point 17 are measured, and whether or not the contact point 17 is appropriately made and broken, is judged on the basis of a change in the resistance value.
In this case, the primary coil 13 of the ignition coil is connected in parallel with the breaker 18, and the impedance of the primary coil 13 is about 0.65 to 0.7 xcexa9. Since the breaker 18 is influenced by the impedance when the breaker 18 is made, the resistance value detected on the breaker 18 when the breaker 18 is broken becomes about 0.65 to 0.7 xcexa9, likewise.
On the other hand, when the breaker 18 is made, the resistance value of the breaker 18 is 0 xcexa9, but since a difference in the resistance between the make and break states is slight, it is difficult to distinguish the make state from the break state, and to judge whether or not the make/break operation is appropriately conducted.
Also, as described above, when the breaker 18 is broken, the low-voltage current in the primary coil 13 is interrupted with the result that a large serge voltage is generated in the secondary coil 14. Therefore, in the case where a detecting circuit and an electronic parts for detection are connected to the breaker 18, since the detecting circuit and the electronic parts cannot withstand the serve voltage, it is difficult to connect the detecting circuit and the electronic parts for detection to the breaker 18.
An object of the present invention is to provide a magneto-system firing apparatus which is capable of detecting an abnormal state rapidly in the case where the breaker is damaged or the like, and there occurs abnormality in the make/break operation of the contact point.
Also, another object of the present invention is to provide a magneto-system firing apparatus that detects the abnormality of the make/break operation on the basis of information related to an angle of a crank shaft of an engine and information related to the make/break operation of the breaker.
In order to achieve the above objects, there is provided a magneto-system firing apparatus, comprising: a magnet fixed to a rotary shaft that interlocks with a crank shaft of an engine; a primary coil to which a low-voltage current that is generated due to the rotation of the magnet is supplied; a breaker which is connected to the primary coil and interrupts the low-voltage current supplied to the primary coil by its break operation; a secondary coil in which a predetermined voltage is induced due to the current interruption caused by the break operation of the breaker to actuate the firing apparatus by application of the voltage generated in the secondary coil; a crank angle detecting portion for detecting the rotating angle of the crank shaft; a breaker make/break state detecting portion for detecting the make/break state of the breaker; and a breaker failure detecting device having a breaker make/break abnormality detecting portion which is capable of detecting the abnormal state of the breaker make/break operation on the basis of information from the crank angle detecting portion and the breaker make/break state detecting portion.
Accordingly, in the present invention, the breaker make/break abnormality detecting portion conducts judgment on the basis of information related to the crank angle outputted from the crank angle detecting portion and information related to the breaker make/break state outputted from the breaker make/break state detecting portion and detects the abnormal state in a case the breaker make/break state is abnormal. As a result, if abnormality occurs in the make/break state of the breaker, the abnormality can be rapidly recognized.
Accordingly, in the case where the magneto-system firing apparatus according to the present invention is employed in an aircraft, if abnormality occurs in the make/break state of the breaker, a pilot can recognize the abnormal state. As a result, since the pilot can recognize the abnormal state of the breaker at a real time, although it is necessary to periodically conduct the inspecting operation of the breaker every 20 hours at the time of inspection on the ground up to now, it is unnecessary to always periodically conduct the inspecting operation in a short period, and the period of the inspecting operation can be lengthened, and the number of times of complicated inspecting operation can be lessened.
Also, according to a second aspect of the present invention, abridge circuit is connected between the primary coil and the breaker, and the breaker is connected with the breaker failure detecting device through a serge voltage preventing means for preventing a serge voltage generated in the primary coil. Also, the crank angle detecting portion includes a magnetic portion disposed on the rotary shaft, a sensor that detects the magnetic portion, and a crank angle detecting means for outputting an electric signal resulting from detecting the magnetic portion by the sensor as an electric signal that represents the rotating angle of the crank. The breaker make/break state detecting portion is so structured as to output the make/break state of the breaker as an electric signal, and the breaker make/break abnormality detecting portion is so structured as to output a predetermined electric signal on the basis of the electric signals outputted from the crank angle detecting portion and the breaker make/break state detecting portion if the make/break operation of the breaker is abnormal.
Accordingly, in the second aspect of the present invention, since the bridge circuit is connected between the primary coil and the breaker, an influence of the impedance of the primary coil to the beaker can be removed. Therefore, since the resistance of the breaker becomes 0 xcexa9 when the breaker is made and infinite when the breaker is broken, the make/break state of the breaker can be readily detected.
Also, since the breaker is connected with the breaker failure detecting device through the serge voltage preventing means for preventing the serge voltage generated in the secondary coil, the influence on the breaker failure detecting device can be prevented, and the abnormal state of the make/break operation of the breaker can be detected without damaging the break failure detecting device.
Also, according to a third aspect of the present invention, the crank angle detecting portion is so structured as to output an electric signal of a high level while the crank moves from a predetermined angular position before a compression top dead center to the top dead center and output an electric signal of a low level while the crank moves from the top dead center to the predetermined angular position before the top dead center, and there is further provided a waveform shaping means for waveform-shaping the electric signal of the high level into a waveform shaping signal representing the predetermined angular position before the top dead center and a waveform shaping signal representing the top dead center.
The spark plug disposed in the piston cylinder is so structured as to fire the air-fuel mixture within the piston cylinder by conducting spark discharge at the predetermined angular position of the crank before the piston reaches the top dead center. Accordingly, in the third aspect of the present invention, in order to judge whether or not the breaker is normally actuated, the electric signal of the high level corresponding to a position of the predetermined angular position before the top dead center of the crank to the top dead center is waveform-shaped and used as information of detecting the breaker make/break abnormality detection.
Further, according to a fourth aspect of the present invention, the breaker make/break abnormality detecting portion compares the waveform shaping signal outputted from the crank angle detecting portion and representing the predetermined angular position before the top dead center with a terminal portion of the electric signal outputted from the breaker make/break state detecting portion and representing the make state, and compares the electric signal outputted from the crank angle detecting portion and representing the top dead center, with the signal outputted from the breaker make/break state detecting portion and representing the break state.
Since the firing apparatus is so structured as to conduct the firing at the predetermined angular position of the top dead center (BTDC) of the crank shaft of the engine, it is necessary that the breaker is appropriately broken when the crank shaft reaches the angular position.
Accordingly, in the second, third and fourth aspects of the present invention, a slight error in the timing of the actual make/break operation of the breaker is estimated, the information of from an angular position slightly lower than the angular position of the crank shaft when firing to the top dead center (TDC) which is predetermined to the engine is grasped by the electric signal of a high level, and similarly information as to the make/break operation of the breaker is grasped by the electric signals of the high level and the low level, and those electric signals are compared with each other to detect the breaker make/break abnormality.
Accordingly, the breaker make/break abnormality detecting portion compares the electric signal representing the predetermined angular position before the top dead center outputted from the crank angle detecting portion, with the terminal portion of the electric signal outputted from the breaker make/break state detecting portion and representing the make state, and judges that the make operation of the breaker is appropriately conducted if the electric signal representing the make state of the breaker is inputted when the electric signal representing the predetermined angular position before the top dead center is inputted. Also, the breaker make/break abnormality detecting portion compares the electric signal outputted from the crank angle detecting portion and representing the top dead center, with the electric signal outputted from the breaker make/break state detecting portion and representing the break state, and judges that the break operation of the breaker is appropriately conducted if the electric signal representing the break state of the breaker is inputted when the electric signal representing the top dead center is inputted.
According to a fifth aspect of the present invention, the bridge circuit comprises a diode bridge circuit, and the serge voltage preventing means comprises a diode. Also, according to a sixth aspect of the present invention, the predetermined angle before the top dead center is 40 degrees. Since the engine for the aircraft is generally so structured as to fire at an angular position of 20 to 26 degrees before the top dead center, when it is judged whether or not the breaker is normally actuated, a reference position for detecting the breaker make state is provided at the angular position near 40 degrees before the top dead center which is before 20 degrees before the top dead center.
In addition, according to a seventh aspect of the present invention, the breaker make/break abnormality detecting portion comprises a flip-flop circuit.